The second ability checks how many creatures have been exiled with Colfenor’s Urn over the course of the entire game.

10/1/2007

The second ability forces you to sacrifice Colfenor’s Urn. If the ability triggers and the Urn isn’t sacrificed (because it left the battlefield or changed controllers, for example), the exiled cards won’t be returned to the battlefield.

10/1/2007

The first ability triggers when a token creature with toughness 4 or greater is put into your graveyard. However, that token will cease to exist before Colfenor’s Plans can exile it.